1. Field of the Invention
The present invention relates generally to head suspensions for rigid magnetic disk drives. In particular, the present invention is a flexure portion of an integrated lead suspension having balanced lead structures that are arranged in such a way that distortion due to changes in the insulator layer is reduced.
2. Description of the Related Art
Head suspensions for supporting read/write head sliders above the rotating media in magnetic disk drives are in widespread use and disclosed generally in the Christianson et al. U.S. Pat. No. 5,461,525. Head suspensions of this type typically include a stainless steel (spring material) load beam having a mounting region on a proximal end, a rigid region having stiffening rails on its opposite sides, a radius or spring region between the rigid region and mounting region, and a gimbal or flexure located on the distal end of the load beam. In the embodiment shown in the Christianson et al. Patent, the flexure is manufactured and formed separately from the load beam and subsequently mounted to the load beam. Other types of head suspensions such as those shown in the Blaeser et al. U.S. Pat. No. 5,198,945 include what is known as an integral gimbal which is formed directly on the distal end of the load beam. The mounting region of the head suspension is adapted to be mounted to a rotary actuator in the disk drive, and typically has a base plate welded thereto for added rigidity.
A read/write head slider is mounted, usually by adhesive, to the flexure of the head suspension. The read/write head sliders are commonly electrically connected to electronic circuitry in the disk drive by lead wires. The lead wires are ultrasonically bonded, soldered or otherwise attached to terminals on the read/write head slider and extend along the length of the head suspension to the mounting region. Tabs are often included on the rigid region and mounting region to secure the lead wires to the suspension. However, lead wires are difficult to attach and add undesirable stiffness and weight to the head suspension.
Alternatives to head suspensions with conventional wire leads are known as integrated lead or xe2x80x9cwirelessxe2x80x9d suspensions. A number of different types of integrated lead suspensions are commercially available. One such type of integrated lead suspension is disclosed generally in the Bennin U.S. Pat. No. 5,598,307. The suspension shown in this patent is fabricated from a laminated sheet of material including a stainless steel spring material layer and a copper conductive layer which are bonded together by a dielectric insulator layer. The load beam and flexure are formed from the stainless steel layer by a photolithographic chemical etching process. The integrated leads are formed from the conductive and insulator layers by a similar process.
The Bennin et al. U.S. Pat. No. 5,491,597 discloses a head suspension which is assembled from a load beam and a gimbal-interconnect assembly. The gimbal-interconnect assembly is etched from a layer of conductive spring material, coated with an insulating dielectric, and mounted to the load beam.
As disk drive technology progresses, head suspensions must be manufactured to more demanding tolerances. Factors that were of secondary importance when tolerances were less demanding are becoming increasingly important. One such factor is how the materials used to fabricate head suspensions react to changing environmental conditions. In particular, dielectric materials commonly used to form an insulator layer of the integrated lead suspension are typically formed from polar polymers which are typically hygroscopic. The use of hygroscopic materials in the insulator layer causes the insulator layer to volumetrically expand in environments with increasing relative humidity. Similarly, the volume of these dielectric materials varies with temperature. Variations in the volume of the insulator layer (caused by hygroscopic and/or thermal stresses) can affect head suspension characteristics such as static attitude.
There is a need for a flexure for an integrated lead suspension that reduces the effects from changes in the insulator layer. To be commercially viable, any such technology must balance several competing design concerns. The integrated lead suspension flexure must be designed with electrical characteristics that facilitate the attachment of and communication with the head slider. In addition, the mechanical characteristics of the integrated lead suspension flexure must be optimized. Flexure stiffness needs to be relatively low in pitch and roll axes to allow proper gimbal action, but relatively high in lateral stiffness to prevent lateral flexure distortion during drive operation. What is needed is an integrated lead suspension flexure that is relatively stable in changing environmental conditions while still allowing for appropriate gimbal action.
The present invention is an integrated lead suspension flexure and method of fabrication. The flexure has balanced integrated lead structures that are arranged and shaped in such a way that distortion due to changes in the insulator layer is reduced.
One embodiment of the integrated lead flexure comprises a metal spring layer having a metal base region, a metal head bonding platform, and one or more metal spring arms connecting the metal head bonding platform to the metal base region for flexure motion. The flexure also includes a conductive lead layer having a surface facing the metal spring layer and extending between the metal base region and the metal head bonding platform. The conductive lead layer has lead base region portions extending over the metal base region and lead suspended portions spaced from and adjacent to at least one of the metal spring arms. The flexure further includes an insulator layer between the metal spring layer and the conductive lead layer having insulator base region portions for bonding the lead base region portions to and insulating the lead base region portions from the metal base region. The insulator layer also has insulator suspended portions on a lower surface of the lead suspended portions and insulator spring arm portions on an upper surface of the metal spring arms adjacent to the lead suspended portions. A first curvature is induced on each insulator suspended portion and a second curvature is induced on each insulator spring arm portion when the insulator layer undergoes volumetric variations. The direction of the second curvature generally opposes the direction of the first curvature, and the second curvature in the insulator suspended portions compensates for the first curvature in the insulator spring arm portions.